The motor products in prior art can be divided into two kinds based upon technical level. One is the traditional AC or DC motor, which have long history and various of types and adopt traditional electric control methods in use; the other one is advanced stepping motor and servo motor, mainly applied to high-precision technical field, such as computer numerical control machine tool, machining center equipment and robot equipment; these products adopt basically control technology with signal feedback, integrated control and man-machine communication as the core.
The traditional AC motor product, which is mature in technology and wide in application, has developed to a degree of technical standard and large-scale industrialization. However, because the functions are simple and low in technical content, these motors have only simple function of transforming electric energy to mechanical energy. In actual application, it requires peripheral circuits and support devices for functions like overcurrent protection, load starting, time control, clutch braking and automatic control and so on. The traditional motors have problems of low value, excessive parts, complex maintenance and high comprehensive cost and so on, and the biggest disadvantage is that the product is difficult to realize technology development and improvement, so it is in urgent need of innovation to adapt new market requirement.
Along with industrial development, the modern high-end product and parts require higher precision. Because of using advanced electrical control technology, the stepping motor has high running precision and using performance, which is much more advanced than the traditional motors. However, the stepping motor also has its disadvantages and boundedness, for example, the stepping motor adopts open loop control, without measuring the speed, so it is low in resolution and control precision; besides, it is low in output power and limited in application range, so it is generally suitable for application of small load.
Based on different rotor structures, three-phase asynchronous motors can be divided into motors with squirrel-cage type rotor and motors with wound type rotor. The squirrel-cage type motor is widely used because of the simple structure, operational reliability, low weight, low price, energy-saving and high efficiency advantages; however, it is difficult to regulate the velocity. Both of the rotor and the stator of the wound type motor are provided with three-phase winding, and are connected with an outer rheostat through a slip ring and an electric brush, thus it can regulate startup performance and rotating speed of the motor by regulating the rheostat; however, it has disadvantages of complex structure, easy-to-damage parts, high price and difficult maintenance problems. At present, application of the traditional three-phase asynchronous motor mainly relies on electric control methods, for example, overcurrent protection, star-delta reduced-voltage starting, and voltage variable frequency starting and so on. The traditional control methods have problems of complex circuit, redundant parts and high maintenance cost. Because the traditional motor is simple in function, low in technical level, without startup protection, overcurrent protection, signal collection and feedback function, the products are difficult to win in the high-end market competition. The traditional motor technology can barely adapt the development requirement of the market.
Because the servo motor adopts closed-loop control method, it is easy to realize speed regulation, torque regulation, stable high-speed running and high position precision, so as to meet various requirements of motor control. However, the servo motor products are complex in structure and circuit and high in production cost; because it is limited by the high-power current, power of the servo motor is relatively small; it is necessary to solve the problems like heat dissipation, magnet isolation, self-locking and light weight of mobile parts before use, so it is complex in use, operation and maintenance; the servo motor is mainly applied on high-precision industrial equipment (for example, CNC and robot), so it is not suitable for common-precision power equipment (for example, production line and general industrial equipment), which is of the highest in demand; the servo motor is high in price, difficult to operate and small in application range; so it is limited in popularization and application. Along with industrial development, the service environment of motors has changed a lot, and the market has higher requirement on motors. Manual operation technology is gradually replaced by automation technology, and the traditional motor cannot meet the requirement of modern industry. The market needs a lot of advanced, innovative, economic, practical, generally applicable, energy-saving and reliable new motors.